add diff-cover to CI

[MathieuLamiot]

Description

Add diff-cover to the CI:

• Pytest runs with the coverage option
• The result is saved as a GH artifact
• A subsequent step is added to the CI to check diff-coverage and reports in the comments.

Type of change

• New feature (non-breaking change which adds functionality).
• Bug fix (non-breaking change which fixes an issue).
• Enhancement (non-breaking change which improves an existing functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as before).
• Sub-task of #(issue number)
• Release

Detailed scenario

The new CI is triggered whenever a new PR is opened. It checks lint & tests (as before, but in 2 separated steps). If tests are successful, diff coverage is computed and reported.

Technical description

Documentation

NA

New dependencies

diff-cover
pytest-cov

Risks

NA

Mandatory Checklist

Code validation

• I validated all the Acceptance Criteria. If possible, provide screenshots or videos.
• I triggered all changed lines of code at least once without new errors/warnings/notices.
• I implemented built-in tests to cover the new/changed code.

Code style

• I wrote a self-explanatory code about what it does.
• I protected entry points against unexpected inputs.
• I did not introduce unnecessary complexity.
• Output messages (errors, notices, logs) are explicit enough for users to understand the issue and are actionnable.

Additional Checks

• In the case of complex code, I wrote comments to explain it.
• When possible, I prepared ways to observe the implemented system (logs, data, etc.).
• I added error handling logic when using functions that could throw errors (HTTP/API request, filesystem, etc.)

[github-actions]

Diff Coverage

Diff: origin/develop...HEAD, staged and unstaged changes

No lines with coverage information in this diff.